Multilayer Analysis of Phan-Thien-Tanner Immiscible Fluids Under Electro-Osmotic and Pressure-Driven Effects in a Slit Microchannel

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Juan P. Escandón ◽  
Juan R. Gómez ◽  
Clara G. Hernández
Keyword(s):  
Flow Field ◽  
Fluid Layer ◽  
Mathematical Formulation ◽  
Velocity Profiles ◽  
External Pressure ◽  
Immiscible Fluids ◽  
Double Layers ◽  
Viscous Drag ◽  
Poisson Boltzmann Equation ◽  
Pressure Driven

Abstract Because the pumping of samples by viscous drag forces and the use of flow-focusing for several sheath flows are widely used in microfluidic devices applications, the present investigation treats about the transport of multilayer immiscible viscoelastic fluids into a slit microchannel by electro-osmotic and pressure-driven effects. The mathematical formulation for the steady-state analysis of the flow field is based on the Poisson–Boltzmann equation and the Cauchy momentum equation. Each fluid layer has independent physical and electrical properties and is formed by a mixture of an electrolyte with a fluid that provides a viscoelastic behavior that follows the simplified Phan-Thien-Tanner (sPTT) rheological model. In the problem, the fluids are conductive and the walls of the microchannel are dielectrics, yielding electric double layers in the liquid–liquid and solid–liquid interfaces; therefore, the flow field is controlled by interfacial electrostatic conditions. The semi-analytical results are centered in the description of the velocity profiles and in the flowrate as a function of a series of dimensionless parameters arising from the mathematical modeling, where we can observe that the multilayer flow characteristics are related to the type of electrolyte solutions, since when the flow field is formed by two or more, interesting interfacial effects appear that modify the shape of velocity profiles and change the magnitude of flowrate in favor or against, depending of the positions of each fluid layer; in addition, the flow raises or diminishes by applying an external pressure gradient.

Interface Analysis of a Combined Electroosmotic/Pressure Driven Flow of Three Viscoelastic Immiscible Fluids in a Microchannel

2017 ◽  
Author(s):  
Juan P. Escandón ◽  
Juan R. Gómez ◽  
Clara G. Hernández
Keyword(s):  
Surface Charge ◽  
Slip Surface ◽  
Flow Behavior ◽  
External Pressure ◽  
Immiscible Fluids ◽  
Charge Densities ◽  
Poisson Boltzmann Equation ◽  
Pressure Driven Flow ◽  
Viscous Stresses ◽  
Pressure Driven

This paper presents the analytical solution of a combined electroosmotic/pressure driven flow of three viscoelastic immiscible fluids in a parallel flat plate microchannel. The mathematical model is based in the Poisson-Boltzmann equation and Cauchy momentum conservation equation. In the steady state analysis, we consider that the three fluids are electric conductors and obey to the simplified Phan-Thien-Tanner rheological model; therefore, different conditions at the interface between the fluids as electric slip, surface charge density and electro-viscous stresses balance are discussed in detail. Results show the transport phenomena coupled in the description of the velocity profiles, by the analyzing of the dimensionless parameters obtained, such as: the electric slips, the electric permittivities ratios, the surface charge densities, the zeta potentials at the walls, the interfaces positions, the viscosity ratios, the viscoelastic and electrokinetic parameters, and the term involving the external pressure gradient. Here, the presence of a net electric charges balance at the interface, breaks the continuity of shear viscous stresses, modifying the flow field; hence, for the established electric conditions at the interface through the values of the electric slips and the surface charge densities, play a role like a switch on the flow behavior. This investigation extends the knowledge about the techniques on the control of immiscible non-Newtonian fluids in microescale.

PIV Measurements of Propeller Flow Field in a Large Cavitation Tunnel

2011 ◽  
Author(s):  
Takayuki Mori ◽  
Risa Kimoto ◽  
Kenji Naganuma
Keyword(s):  
Flow Field ◽  
Velocity Profiles ◽  
Marine Propeller ◽  
Measured Velocity ◽  
Piv Measurements ◽  
Tip Vortices ◽  
Systems Research ◽  
Tracer Particles ◽  
Cavitation Tunnel ◽  
Blade Tip

Flow field around a marine propeller was measured by means of PIV technique in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense, Japan. Test section of the tunnel is 2m(W) × 2m(H) × 10m(L) and it contains 2000m3 of water. 2-dimensional PIV (2-D PIV) and stereo PIV (SPIV) measurements were made for a five-bladed highly skewed marine propeller. In the case of 2-D PIV measurements, high spatial resolution measurements were possible by seeding relatively small amount of tracer particles. Phase-averaged flow fields showed details on evolution of tip vortices. In the case of SPIV measurements, much larger amounts of tracer particles were required, and it was difficult to perform high resolution measurements. Phase averaged velocity profiles from SPIV measurements showed good agreement with 2-D PIV-measured results. PIV-measured results were compared with results of LDV measurements. Although PIV-measured velocity profiles showed fairly good agreements with LDV-measured results, some discrepancies were found at the blade tip region.

Approximate Analytical Solutions for Marangoni Mixed Convection Boundary Layer

2010 ◽  
Author(s):  
Yan Zhang ◽  
Liancun Zheng ◽  
Jiemin Liu
Keyword(s):  
Boundary Layer ◽  
Mixed Convection ◽  
Analytical Solutions ◽  
External Pressure ◽  
Immiscible Fluids ◽  
Temperature Fields ◽  
Convection Boundary Layer ◽  
Coupling Condition ◽  
Approximate Analytical Solutions ◽  
Convection Boundary

The paper deals with a steady coupled dissipative layer, called Marangoni mixed convection boundary layer, which can be formed along the interface of two immiscible fluids, in surface driven flows. The mixed convection boundary layer is generated besides the Marangoni convection effects induced flow over the surface due to an imposed temperature gradient, there are also buoyancy effects due to gravity and external pressure gradient effects. We shall use a model proposed by Chamkha wherein the Marangoni coupling condition has been included into the boundary conditions at the interface. The similarity equations are first determined, and the approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade´ approximant technique. The features of the flow and temperature fields as well as the interface velocity and heat transfer at the interface are discussed for some values of the governing parameters. The associated fluid mechanics was analyzed in detail.

Simulation of Flow and Mass Transport in a Meander Microchannel Subject to Electroosmotic Pumping

2003 ◽  
Author(s):  
Dominik P. J. Barz ◽  
Peter Ehrhard
Keyword(s):  
Mass Transport ◽  
Double Layers ◽  
Complex Flow ◽  
Electrical Field ◽  
Electrical Fields ◽  
Electrical Double Layers ◽  
Electroosmotic Pumping ◽  
Pressure Driven Flow ◽  
Flow And Mass Transport ◽  
Pressure Driven

We have investigated the flow and mass transport within an electroosmotically-pumped incompressible liquid through a meander microchannel system. We employ two-dimensional, time-dependent Finite Element simulations in conjunction with a matched asymptotic treatment of the electrical double layers. The electroosmotic pumping is realized for two idealized and two realistic electrical fields, while a pressure-driven flow is used for comparison. We focus on the aspects of the electroosmotic transport. We find for most of the electroosmotically-driven cases rather complex flow fields, involving recirculation regions. These recirculation regions in all cases increase dispersion. (i) The least dispersion is associated with a plug-type velocity profile, which is obtained for an idealized purely wall-tangential orientation of the electrical field. (ii, iii) We find that both, the idealized horizontal electrical field and the real electrical field between two vertical plates give considerably higher dispersion than the pressure-driven flow. Vertical plate electrodes, therefore, do not allow for a electrical field, which minimizes dispersion. (iv) The arrangement of two point electrodes at the in and out sections likewise proves to be no optimal means to reduce dispersion beyond the pressure-driven flow. Thus, meander geometries of channels, in general, cause severe problems if electroosmotic pumping needs to be achieved in combination with minimized dispersion.

Effect of intermediate fluid layer on Kelvin–Helmholtz instability

2018 ◽  
Vol 96 (10) ◽  
pp. 1145-1154 ◽  
Author(s):  
Ying Zhang ◽  
Wenqiang Shang ◽  
Mengjun Yao ◽  
Boheng Dong ◽  
Peisheng Li
Keyword(s):  
Growth Rate ◽  
Stokes Equations ◽  
Fluid Layer ◽  
Immiscible Fluids ◽  
Navier Stokes ◽  
Helmholtz Instability ◽  
Flow Configuration ◽  
Front Tracking Method ◽  
Internal Disturbance ◽  
Over Time

Two-dimensional K-H (Kelvin–Helmholtz) instability of the three-component immiscible fluids with an intermediate fluid layer is numerically studied using the front-tracking method (FTM). The instability is governed by the Navier–Stokes equations and the conservation of mass equation for incompressible flow. A finite difference method is used to discretize the governing system. This study focuses on the influence of flow configuration, the thickness of intermediate fluid layer and the distribution of intermediate fluid layer on K-H instability. It is shown that the larger the initial horizontal velocity difference is, the faster the internal disturbance increases, and the characteristic form of K-H instability becomes more obvious for different flow configuration. It is also observed that the thickness of the intermediate fluid layer is negatively correlated to the billow height and the numerical growth rate. In addition, when the intermediate fluid layer is thicker than 0.4 times the disturbance wavelength, the billow height and the numerical growth rate for the K-H instability of the upper and lower interfaces change over time synchronously. The higher the initial height of the lower interface is, the greater the growth rate and billow height of the upper interface are. Besides, the upper and lower interfaces are rolled up synchronously over time when the intermediate fluid layer is symmetrically distributed with y = 0.5 in the fluid system.

Analysis of Mixed Convection in a Vertical Channel in the Presence of Electrical Double Layers

2018 ◽  
Vol 73 (8) ◽  
pp. 741-751 ◽  
Author(s):  
Niazi M. Dilawar Khan ◽  
Hang Xu ◽  
Qingkai Zhao ◽  
Qiang Sun
Keyword(s):  
Mixed Convection ◽  
Electrical Potential ◽  
Vertical Channel ◽  
External Pressure ◽  
Double Layers ◽  
Convection Flow ◽  
Analysis Method ◽  
Flow Models ◽  
Electrical Double Layers ◽  
Homotopy Analysis

AbstractWe consider the fully developed mixed convection flow in a vertical channel driven by an external pressure gradient and buoyancy force. Unlike in previous studies, we employ a new model to formulate the flow problem that guarantees the smoothness and continuity of the distributions of the electrical potential and velocity. This model, solved by the homotopy analysis method, is compatible with the channel flow models commonly used in fluid mechanics.

Numerical Simulation on the Electrophoretic Motion of Multiple Particles in Microchannels

2004 ◽  
Author(s):  
Chunzhen Ye ◽  
Dongqing Li
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Electric Field ◽  
Particle Motion ◽  
Outer Region ◽  
Numerical Results ◽  
The Other ◽  
Double Layers ◽  
Rectangular Microchannel ◽  
Moving Particle

This paper considers the electrophoretic motion of multiple spheres in an aqueous electrolyte solution in a straight rectangular microchannel, where the size of the channel is close to that of the particles. This is a complicated 3-D transient process where the electric field, the flow field and the particle motion are coupled together. The objective is to numerically investigate how one particle influences the electric field and the flow field surrounding the other particle and the particle moving velocity. It is also aimed to investigate and demonstrate that the effects of particle size and electrokinetic properties on particle moving velocity. Under the assumption of thin electrical double layers, the electroosmotic flow velocity is used to describe the flow in the inner region. The model governing the electric field and the flow field in the outer region and the particle motion is developed. A direct numerical simulation method using the finite element method is adopted to solve the model. The numerical results show that the presence of one particle influences the electric field and the flow field adjacent to the other particle and the particle motion, and that this influences weaken when the separation distance becomes bigger. The particle motion is dependent on its size, with the smaller particle moving a little faster. In addition, the zeta potential of particle has an effective influence on the particle motion. For a faster particle moving from behind a slower one, numerical results show that the faster moving particle will climb and then pass the slower moving particle then two particles’ centers are not located on a line parallel to the electric field.

Numerical and Experimental Studies on Electrical Potential Distribution of Pressure Driven Flow in Parallel Plate Microchannels

2004 ◽  
Author(s):  
Fuzhi Lu ◽  
Jun Yang ◽  
Daniel Y. Kwok
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Parallel Plate ◽  
Potential Distribution ◽  
Continuity Equation ◽  
Electrical Potential ◽  
Double Layers ◽  
Linear Potential ◽  
Pressure Driven Flow ◽  
Pressure Driven

A number of papers have been published on the computational approaches to electrokinetic flows. Nearly all of these decoupled approaches rely on the assumption of the Poisson-Boltzmann equation and do not consider the effect of velocity field on the electric double layers. By means of a charge continuity equation, we present here a numerical model for the simulation of pressure driven flow with electrokinetic effects in parallel-plate microchannels. Our approach is similar to that given by van Theemsche et al. [Anal. Chem., 74, 4919 (2002)] except that we assumed liquid conductivity to be constant and allows simulation to be performed in experimental dimension. The numerical simulation requires the solution of the Poisson equation, charge continuity equation and the incompressible Navier-Stokes equations. The simulation is implemented in a finite-volume based Matlab code. To validate the model, we measured the electrical potential downstream along the channel surface. The simulated results were also compared with known analytical solutions and experimental data. Results indicate that the linear potential distribution assumption in the streaming direction is in general not valid, especially when the flow rate is large for the specific channel geometry. The good agreement between numerical simulation and experimental data suggests that the present model can be employed to predict pressure-driven flow in microchannels.

An Experimental and Analytical Investigation of Rectangular Synthetic Jets

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Gopi Krishnan ◽  
Kamran Mohseni
Keyword(s):  
Flow Field ◽  
Turbulent Jets ◽  
Velocity Profiles ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Empirical Modeling ◽  
Transition To Turbulence ◽  
Two Dimensional ◽  
Limited Region ◽  
Velocity Decay

In this paper the flow field of a rectangular synthetic jet driven by a piezoelectric membrane issuing into a quiescent environment is studied. The similarities exhibited by synthetic and continuous turbulent jets lead to the hypothesis that a rectangular synthetic jet within a limited region downstream of the orifice be modeled using similarity analysis just as a continuous planar jet. Accordingly, the jet is modeled using the classic two-dimensional solution to a continuous jet, where the virtual viscosity coefficient of the continuous turbulent jet is replaced with that measured for a synthetic jet. The virtual viscosity of the synthetic jet at a particular axial location is related to the spreading rate and velocity decay rate of the jet. Hot-wire anemometry is used to characterize the flow downstream of the orifice. The flow field of rectangular synthetic jets is thought to consist of four regions as distinguished by the centerline velocity decay. The regions are the developing, the quasi-two-dimensional, the transitional, and the axisymmetric regions. It is in the quasi-two-dimensional region that the planar model applies, and where indeed the jet exhibits self-similar behavior as distinguished by the collapse of the lateral time average velocity profiles when scaled. Furthermore, within this region the spanwise velocity profiles display a saddleback profile that is attributed to the secondary flow generated at the smaller edges of the rectangular orifice. The scaled spreading and decay rates are seen to increase with stroke ratio and be independent of Reynolds number. However, the geometry of the actuator is seen to additionally affect the external characteristics of the jet. The eddy viscosities of the synthetic jets under consideration are shown to be larger than equivalent continuous turbulent jets. This enhanced eddy viscosity is attributed to the additional mixing brought about by the introduction of the periodic vortical structures in synthetic jets and their ensuing break down and transition to turbulence. Further, a semi-empirical modeling approach is proposed, the final objective of which is to obtain a functional relationship between the parameters that describe the external flow field of the synthetic jet and the input operational parameters to the system.

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